Abstract
Iron deficiency anemia (IDA) has long-lasting effects on cognition and behavior in humans, even into adolescence. Sleep disturbances are common in adolescence and rapid eye movement (REM) sleep is thought to be important for memory consolidation. No study has assessed for an additive effect of REM deprivation (REMD) on learning and memory after IDA during development.
Objective: To assess the effect of REMD on spatial learning and memory in rats that were iron sufficient (IS) or iron deficient (ID) during development.
Methods: IS (13) or ID (11), 40-day-old Sprague Dawley rats were randomly assigned (within diet group) to REMD or no REMD (REM-sated - REMS) treatments. ID rats began an IS diet on day 1. Hematocrit and serum iron were measured for all rats every 3–4 days. REMD consisted of 6 hours during the light cycle for 20 consecutive days. All rats had 8, 1-minute daily swim trials in the Morris watermaze and latency, speed, path length, and thigmotaxis (tendency to stay along the wall) were measured. On day 21, a single 1-minute probe trial was performed. Measures were compared by diet and treatment using Student's t-test and repeated measures ANOVA with significance p<0.05.
Results: ID hematocrit and serum iron were significantly lower than IS rats on d1 (F=67.773, p<0.001; and F=76.235, p<0.001, respectively), but reached IS levels within one week. Overall, IS rats swam faster than ID rats (F=6.487, p<0.02) and REMD rats swam faster than REMS rats (F=7.077, p<0.005). Controlling for swim speed, ID-REMD rats had shorter latencies than ID-REMS rats (weeks 2–3) (F=3.498, p<0.04). Latencies did not differ with REMD treatment for IS rats. There was a trend for ID-REMD rats to have a shorter path length compared to ID-REMS rats and for IS-REMD rats to have a longer path length than IS-REMS rats (F=2.721, p<0.08). Path length in the platform quadrant was greater for ID-REMD versus ID-REMS rats (week 3), and for IS-REMS versus IS-REMD rats (week 2) (F=5.042, p<0.02). Overall, ID rats had greater thigmotaxis than IS rats (F=14.910, p<0.002). REMD reduced thigmotaxis for ID rats (d13–20, F=6.755, p<0.005) but did not affect this measure for IS rats. On the probe trial, there were no significant differences by diet or REMD treatment.
Conclusion: Iron deficiency during development adversely affects performance in a spatial learning task. Paradoxically, REM deprivation appears to improve performance for formerly ID rats. Further work is needed to understand whether cognitive or non-cognitive factors underlie this improvement.
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Hurst, A., Dimitrijevic, M., Lee, M. et al. 4 Iron Status, REM Deprivation and Spatial Watermaze Performance in Rats.. Pediatr Res 58, 816 (2005). https://doi.org/10.1203/00006450-200510000-00034
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DOI: https://doi.org/10.1203/00006450-200510000-00034